1. Field of the Invention
This invention relates to a device for setting an electric command variable and, in particular, to a device which includes digital-to-analog converters which are connected in parallel and which have analog outputs signals which are valued by means of electrical resistances.
2. Description of the Prior Art
A device of the above-described type is known from the article "Digital-Analog Converters with FET Switches" (in German) published in Elektronik, 1972, No. 2, Pages 39-43. This known device comprises three digital-to-analog converters which are connected in parallel and have analog output signals which are valued in powers of 10.
A disadvantage of the aforesaid known device results from the general property of a digital-to-analog converter of furnishing an output signal whose error equals one half the value of the bit position of minimum valuation of the converter. In particular, when an overflow jump occurs, i.e., when the limits of the conversion range of a digital-to-analog converter are exceeded or fallen short of, with the resulting variation of the setting of the digital-analog converter of next higher valuation, this results in a jump error, i.e. a setting error of the analog command variable.
The primary object of the present invention is thus to provide a device of the above-mentioned kind, in which the command variable can be varied from the value set after an overflow jump without the occurrence of further overflow jumps and the jump errors connected therewith.